Hi,
I suggest you to create midi plugin where we can in easy way (visually drug and drop) assign midi notes from keys to the various pads to play drums from various drum samplers. You have piano keys on top and pads bottom. Piano keys are assigned typically to the samplers and pads are assigned to the external device (pads). You do drag and drop from keys to pads and voilà . Of course we have different devices with pads so to be flexible you can create possibility to change a set of pads in this midi plugin